Sheetsxsheet i



1951 A. R. VAN c. WARRINGTON 23,430

ELECTRONIC RELAY ARRANGEMENT FOR PROTECTING POWER SYSTEMS Original Filed Oct. 14, 1948 2 SHEETS-wSHEET 1 Fig.5.

Inv'entor": 9 Albert R. van C. Warringtbn His Attorney.

R by

Nov. 20, 1951 A. R. VAN c. WARRINGTON 23,430

ELECTRONIC RELAY ARRANGEMENT v FOR PROTECTING POWER SYSTEMS Original Filed Oct. 14, 1948 2 SHEETS-SHEET 2 l I l i g l i X J & 1

(( 1005 {st-0'} +1 E l 4 I f -fr lcosfwj Fig.6.

lH-K T Inventor": Albert R.van Qwarf'ington,

His Attorney.

Reissued Nov. 20, 1951 ELECTRONIC RELAY ARRANGEMENT non PItQ'lQEQTINQ POWER SYSTEMS.-

Albert R. yan .C. Warrington, Staflordshire, Eng: land, assi nor. to. G l ctr C m ny. a

corporation of York Original-No. 251L680, dated-I 11m}, 13,. 1959,. Serial; No. 54,533, October 14, 1348, ppli catign for reissue June .9, 1951, Serial No. 230$??? 13. Clainz1 s, (Cl.175-294)- Matter enclosed in heavy brackets lf ilappearsin the original patent but forms no part. 01. this reissue specification; matter printed in italics indicates theadditions made by reissue.

My invention relates tolelectronic. relay arrangements for. protecting. power. systems and .more particularly to. a Protective arrangement to. the assignee of this invention, thereis" dis-- closedand claimed a relay arrangement wherein electromagnetic relays of the so-called wattinetric type are utilized to protect an electric power system h r l s of this wa ns o naten es the well-known mho type."

'In the' United States Letters p t nbzzz ps Biv'ens', granted @October 20; 19.42, and assigned to the assignee of this application. there is. disclosed a protective appaffltus 'utili'zingi'electronic valves for, protecting electric powerjsysnems; My invention constitutes an improvement of meal:- rangement disclosed and claimed injthe abovem nti n dv v n a n a s mila t the arran eme d sclosed in. th abovmm ntionesi Warrington patent that it is adapted to be applied to a power, system in substantially the .s arfne way and in that. the relay itself is of the mho type. Also my invention is related; to the n ti n d cl s d and. claim d n a sli afiqn Seri Numb r 43 8 e octgher .1 9 Mac h s si ed t tlieas isn e f mis inpli cation.

n obj ct of my en on. is to m d an improved electronic relay having 'rapid' and unchanging time characteristics so that a fault condition may be cleared promptly irrespectiveof the distance from the fault to the relay.

Another object of my invention is the provision of a relay having more precise operating characteristics than presently-known devices;

Still another object of my invention is to-provide an electronic mhojrelay'whose characteristic impedance circle may be offset from the origin of the impedance diagram so-that the relay willbecapable of reaching up and-down the power lineeven though the relay is primarily-directional in character.

A further object of my inventionis the provision of relay having'an impedance characteristic which may readily-be offset so as to afford reach in one direction 'without interfering with the reach settingo'f the relay in the other direction.

A still further object of my invention is to provide a relay arrangement wherein a gaseous QLI 2... discharge tube is utilized to control the trip circuit of an interrupter in response to the brief impulse which is providedv by a vacuum tube which is responsive to a fault condition and which together with other circuit elements servesito m ar he. partic r m eda c e ist t to the relay.

A. re a an m nt mbed-ri m i nt comprises three essential components; 1,. .et, a i sc fl t a nul in ln r u an stripn circuite manning c r u q prise means for producing'a voltage which is a functionor. theisystem vol means br odu ng a voltage dependent u n the system current, andme'ans for comparing the setwovoltages and supplying the resultantjvoltageto. the control s n a sl mentvacuum ub I heisstantaneous values of system voltage and current bear a predetermined relationshi one to" the other which relationship is indicativeofa fall condition on the power system, the hpld ofi'bia's of the control grid will: beovercome; The'pulsing circuit comprises a peaking transformer and an 'electronicvalve responsive to system 'voltageffo'r energizing thesuppressor gridof the pentode at themaximum instantaneous value of the system voltage. Thus the pentode will conduct. at the instant when the system voltage is a maximum if .ap redetermined voltage resulting from a sysm falll is sup lied to thecontr l g id the, o by the "measuring circuit. The tripping cir; it includes means for energizing the trip coil of "a circuit br ak s q at diwi h the nmtsc ed in ti nli I l n th flew of current tli' puah th 'p n dle- As i "h exnl i lmqre an hereinafter, a relay arrangement em Od Iig my invention is oh 'cterizfed by a circular impedance charactis o well known in connection with electromag etic mhorelays; In accordance with avfurt her featureoi my invention, I provide mansion of setti th h c rcle ro th i n wh c m rises mean f ser int the pulsing'fcircuit'an electrical quantity producedby the system current.

'In the following description myinvention is set forth in" connection with a-mhorelay but it will be understood that it is equallyapplicable to other types of relays. For example, instead of producing a voltage by comparing a voltage derived from. the power system current. with a voltage derived. fromthe; power system; voltage, the control. voltage could be. Produced by comparing two. voltages both of which are depBhdfiQi upon various. otherfeleetrical quantities, such, tor example, as. .theecurrentientering.anddeaying Patent 2,405,081. stood by those skilled in the art that the arrange- 'ment of Fig. 1 would comprise an Ml or an M2 vmho relay unit as explained in the above Warrington patent.

Iacross line conductors 2 and 4. secondary winding from current transformer l is supplied to the primary winding of the transactor unit 6. Transactor unit 6, in effect, is a 'Ico'mbined reactor and transformer. A resistor 1 Lisconnected across the terminals of the secondary vwinding 8 of the transactor 6. ,of the voltage across resistor I is impressed across iresistor element 9 and capacitor element In by .suitable' adjustment of the sliding contact I I. In

a protected piece of electrical apparatus, or section. of power line. Furthermore, the instant at which the suppressor grid is energized need not be at the peak of the system voltage but could be at some other time such for example at the.

zero point of the system current in which event the relay would be of the reactive type.

My invention will be better understood from the following description vwhen taken in connection with the accompanying drawings and the scope of the invention will be pointed out in the appended claims.

In the accompanying drawings, Fig. l is a diagrammatic representation of the various circuit elements comprising my invention, Fig; 2 is a family of curves to aid in explaining the operatlon of the circuit of Fig. 1, Fig. 3 is an imped- "ance diagram to aid in explaining the characteristics of the circuit shown in Fig. 1, Fig. 4 is a diagrammatic representation of the circuit elements embodied in my invention wherein means are provided for modifying the circuit of Fig. 1 to produce an offset impedance characteristic, 5 is a vector diagram to aid in explaining .Ythe principles of the circuit shown in Fig. 4, and Fig. 6 is an impedance diagram also for the purpose of aiding in explaining the circuit elements .of Fig. 4.

It will be obvious to those skilled in the'art that the circuit shown in Fig. 1 comprises an arrangement for protecting two conductors of a ,transmission line. other arrangements identical to the arrangement It will be understood that two or Fig. 1 would be necessary to afford protection for example, for a three-phase transmission line as explained in the above-mentioned Warrington Furthermore, it will be under- The measuring circuit of Fig. 1 will now be described. A current transformer l is energized in jaccordance with current flow in line conductor 2 j and one winding 3 of a potential transformer is energized in response to the voltage appearing Energy from the A selected portion this way a voltage which is a function of the sys- To overcome this objectionable tendency which would distort the relay impedance characteristic, a capacitor I3 is connected across thesecondary winding I 2 to neutralize this effect, because the voltage across capacitor I3 is in- .versely proportional to the frequency as is well known.

As explained above, the voltabe E1 is compared with a voltage which is a function of the system voltage. The system voltage applied across the primary winding 3 of the potential transformer 1! establishes a voltage in the secondary winding 1 ii of the transformer II. This voltage, dependent on the system voltage, may be represented by th expression E sin wt and is indicated in Fig. 1. Thus, when the voltage E sin wt is bucked against the voltage E1, the resultant voltage will determine the potential of the control grid I9 of the pentode 20 since the control grid I9 is connected to the measuring circuit through the conductor 2| and the schematically-represented sliding contact 22. In practice I have found it desirable to arrange the circuit so that the control grid I! will prevent the pentode 20 from conducting whenever the voltage E sin wt' is greater than the voltage Er so that the control grid I!) will allow the pentode to conduct if these two voltages are equal or if Er exceeds E sin wt.

While the tube 20 is shown on the drawings and referred to in the description as a pentode it will be obvious that an electronic device having a different arrangement and number of electrodes could be used provided that the measuring and timing voltages are utilized as explained above without departing from my invention. For example, the screen grid 49 is connected to the positive bus 43 through the resistor 50 and is merely for the purpose of improving the amplifying characteristics of the tube 2|] but does not affect the invention.

The function of the measuring circuit above described will be better understood with reference to Fig. 2. In Fig. 2 the relay voltage E sin wt is proportional to and in phase with the system voltage. Therelay current I sin wt is likewise proportional to and in phase with the current in conductors 2 and 4 and lags the relay voltage E sin wt by the system power factor angle t. The letter represents the power factor of the line during fault conditions. This is because there is negligible angular'shift in these quanti- In practice it isdesirable to have the angle of maximum reach occur at some angle between 45 and '75 degrees from the Raxis. To this end the natural angle of. the transactor 8 and a means comprising the capacitor [0 and the resistor 9 are utilized to cause the voltage E1 to shift by an angle 0. In addition the polarity of transactor I is reversed so that E1 is directly out of phase with E sin wtat the system power factor angle and the angle of maximum reach occurs at the angle 0. When this is done, the respective magnitudes ,of the voltage E1 and the voltage E sin wt will determine the potential applied to the control grid IQ of the pentode 20. The resistor 23 is merely for the purpose of preventing damaging current flow through the conductor 2i under abnormal conditions.

.. As explained above, it is desirable to have the pentode 20 conductive at the instant when the line voltage E sin wt is a maximum. To this end the above-mentioned pulsing circuit is used wherein the secondary winding 24 of the transformer II is utilized to control the potential of the grid 25 of the trlode 26 through resistor 21.

3 ,4 6 dine-triads 25 hascharacteristicssuohithat it will linel-toelinelsiol-tagesexist memory action saturate inresponseto arelativelylsmall. change am,-provided-..v 'Iihismemoryeaotidnarrangement in;potential:of theigrid- 25 so that the tube will is7accomplished1by'the tuned: circuit comprising nduct-heavilyv n, ho h h p ential. supthe primary winding 2st oftlthe peakingritransr plied to grid25. is quite low as would be the case former 29 and the canagit0r .33; In this W y 1a "produced by the peaking transformer 29 1s reprepulsing t ircuits already described, the tripping;

"lt w ill beseen that-the peaking transformer Vfipltpentode when made'su when aphase-to-phase fault involving conductors memory action peak for sile'ral cycles is mair 2 and {occurs very close to th lay Iheplate tained after the fault occurs. Thus, ample time cir c u it oi def 2 v jihcludesthe pi'imarywindis provided for energizing the suppressor grid 32 ing 28 of'peak'i'ng transformer 29. The secondary of the pentode 20 to allow 'thetripping circuit 01' winding of peaking transformer fl is co'r'i- 21 associated, breather to i become nected throngharpsistor 3 l tq,the;suppressor 'ei'iergi'z'd.

g rig y 0g v eritpde' 20 and also to 'therela- When the pentcde 20 is rendered conductive by tively "largebiasinipotential 5|. The voltage means of the operation-ioft the measuring and sehted in Fig. 2 by t he curve E g. mom Fig.2 ,15 'circiiitfwlill hefenergized spec ag'e E t occurs when the voltage E si'n' wt is a has a bri ei pulseoi current in maximum.' Tlois is de s irable.because experience cir tfand ca 'ses thefggaseo has shown that a great majority of fault congliit tihris" are initiated 'at or just before the instant when the line voltage is a maximum." 'Furth rmore, as willbe more fully eiimaii e nerei a a circular impedance characteristic isechieved by selecting the maximum instantaneous value of the line voltage as the instant when the pulsing circuit energizes the suppressor arid -32 of pentode 20 so as to-ove'rcorne the large" bias of th pote'ntial 5 land therehy to allow the pento de P I 20 to conduct provided the'pot'ential-supplie'd to qi sie ridlinfih ll ing oh the control grid l 9;9f thepentodejfidsindicative tam-me the conditions i faint endifi n 0}} t 3 1 11? mpr sin 9Q? ductors' 2' and 4. The voltageEet produced'by the peaking transformer actually is utilized only at the instant of positive voltage maximum at the line voltage due'to the inherent characteris- I tics of the triode 26. It will be understood-'by those skilled in theart that another triode such as 26 could be utilized t o energize another peaking igas filled tube fires dueto the action oitransformer similar to 25 when the line voltage is cz' pafl tpr 42: when the, p t-Ode '20 P 555 5- P185199 2. maximum negative value so that a pulse would 40 Wlifii mally, QQPEQ QE 3- 1%; mpre sed occur every half cycle as shown 'in'Fi'g. 2; For BQQXS iQ QSS lFitgB fiq al to the vq ag b purposes of simplicity, this adglitiorial triogle is weenf he ega iye bus l1andjthe.positivebus fli not shown in Fig. 1,. ItwilI be understood by When PQ lt-QQQmi lisnderedc nqllttive, a at'e those sk i lledin the art that the peak occurring i? l it fi fl wsuthrp h IQ, 5. 3 M- The at the negative half cycle of E" sin wt can be ol a rop h u h. to 3. a se t e no: utilized toallow an additional pentode similar to initia of he u er l e of ha -a t L to zp t t conti ti e, The control i o t e ge. q i l re u e pe t e s not th ditional pentode would be supplied wit H flff llg 1 1 1 he capamtor 42 mayd sz axse siifiiia'rj to E1 escepttreversed'inf'po quw s a e t er a rne ai tai d or ameai he el y wit .nqesqrt ied wait! brief- FW we W i a e measure the line impedance once each half cycle i a a at tet 42 1S P m t se i and during fault conditions would operate within tlve to the gnd 1510f h -a T k t -fifi qt one half cycle after the OcEurrence of, the-fault; renders 1rthe cathode of the triode 34 mere megaa e p tart hesitates?that tits; uring e negaive or posiive a cyce o i system voltage E sin wt. gg gfgzgigggfiggisgg the k??? 1' As mentioned above, the triode amplifier 2B arranged so that it saturates when a relatively; i gg out t 3 t mtsq we i h tte Small grid voltage is applied thereto. Thus, a 1% earthy-{em 1 w s s i relatively constant peaking voltage 0 011 28 acros wig! P }Q-P e onlglnial'r th r ei the secondary winding 30 of the peaking transtfggg a t v h f. T 19: former 29 even though the voltage applied td the V0 Whlch 1s a f 9 mh grid 25 of the triode. 26. may vary over a rielarent may be express.ed'

tively wide range. In this way, uniform potentials are applied to suppressor grid 32 of pentpde 55 m. l?

2D and attendant consistency of operatihnds here. K. S e at Of-the asur ngircu tachieved should thei f ult bq Wiminthe and where is the. power'factor. angle.. ahd. 0. s zone, for example, theMl .unit mightfiotoperate h? an the m a i 3 79 a he? properly if the, fault within zone I were close P 5 e er ds c i l -im fil" 5E enoughto the MI unit to cause the line voltage to con/F101 gmd 15 conaemfadi h h l h bgtmegn conductors} and): toldmpbelowl a pm: derived, from the. current in the, power system determined minimum value in which eventthe .elgual thie'voltaigei l t dr'ivd frolill'th triode 25 would not fire. For. the purpose: of syfitgm-volpagf" (mam-119165 m t a making, sure that'thetriode amplifier 26.will fire [KI sin wt (--0)=E sin-wt} in respqnsetq a fault-conditionwhen veryilow Li KI sin- [wt'(r0)-l=Esiwwt- Since the pentode 20 is held on by the suppressor grid 32, except when the line voltage is a maximum, i. e., when wt equals 90, the above equation may be written as follows:

2 E=KI cos (-0) which is the impedance Z measured by the relay so that 4 Z=K cos (vs-) Equation 4 is a circle of diameter equal to K which circle represents the impedance characteristic of a mho relay.

In Fig. 3 the quantities appearing in Equation 4 are graphically represented. From Fig. 3 it is obvious that changes in the angle 0 of the measuring circuit will merely shift the circle clockwise or counterclockwise about the origin of the X-R diagram, and that; changes in the power factor angle will merely change the value and angular dispositionof the impedance Z. Because .the impedance Z forms one leg of a right triangle and because the diameter K of the circle forms the hypotenuse of the triangle, changes in the magnitude and angular disposition of the quantity Z will not. destroy the circular characteristic of the relay.

As explained in the above-mentioned Warrington Patent 2,405,081, for example, it is desirable to cause a mho relay unit M3 to have a characteristic which is offset with respect to the origin so that the relay is capable of reaching in the opposite direction along the transmission line from that of the reach of the mho relay units MI and M2. To this end the circuit arrangement shown in Fig. 4 may be used. The circuit of 4 is identical to the circuit of Fig. 1 except that in Fig. 4 means are provided for shifting the peaking voltage produced by the pulsing circuit with respect to the voltages produced by the measuring circuit. To this end a secondary winding 46 is added to the transactor 6 and the voltage developed across this secondary winding is applied to a resistor 41 connected in series with at capacitor 48. The voltage developed across the capacitor 48 is supplied between the cathode of the triode 26 and the secondary winding 24 of the potential transformer l4. This voltage may be representedby the expression:

where K0 is a constant converting line current to offsetting voltage in the transactor and where d: is the system power factor and 0' is the relay angle of the oifsetting voltage.

The total voltage impressed on grid 25 of tube 26 is the vector sum of the voltage across resistor 41 and capacitor 48 and the voltage E sin wt may be expressed as follows:

The vector sum of the above two quantities which are combined to produce the pulsing tube voltage will be a maximum at some point on the system voltage wave E sin wt other than the maximum point. Thus, because the sum of'the two quantities represented by Equation will cause by means of the peaking transformer 29 in the plate circuit of tube 26 the suppressor grid 32 of pentode 20 to allow pentode 20 to conduct during fault conditions when the vector sum of these two quantities is a maximum it is necessary Rearranglng This expression may be shown on a vector diagram as in Fig. 5. From the vector diagram it is seen that the instantaneous value of voltage applied to the grid of tube 26 may be expressed as 8 Vpt=Vpt sin (WlH-a) where a is the angle between the reference vector E+KoI cos (-0) and Vpt- Equation 8 is a maximum when sin (Wt+a) =1 or when wt+a=. It follows that which indicates the time when the pentode in the tube circuit will be gated and allow comparison of line voltage and line current. It is apparent from Equation 9 that 10 cos wt=sin a and sin wt=cos a from the vector diagram in Fig. 5 it is seen that 11 cos E+K I cos 5-11) and sin K I sin (s-0') To facilitate substitution, Equation 1 may be expanded as follows [E sin wt=KI sin wt cos (-9) +cos wt sin (-0)] 12 E sin wt=KI [sin wt cos (0) cos wt sin (0)] Theexpressions for sin wt and cos wt as shown in Equations 10 and 11 may now be substituted in Equation 12 and the expression for an offset mho type impedance circle derived as follows This equation can further be developed to show that it is that of an offset mho type impedance circle. To simplify the development, however. the relay angle 0 will be assumed equal to the angle. of the offsetting voltage .0; since this is generally true in the application or mho type" relays Equation 14ma'y now be written (K ray to each side of theequation which is recognized as the equation of an offset mho type impedance circle with diameter 'equal to -K+Ko of which K is the offset'and K is the original diameter before offset. Equation 19 is shown diagrammatically in Fig. 6.

It should be notedfrom Fig.-6-that the portion K of the diameter of the mho impedance circle is identical to the diameterof the mho impedancecircle shown in'Fig. 3. Stated otherwisethe offset is achieved by enlarging'the characteristic circle of a relay such as that shown in Fig. 3 without changing the reach-of'the unit in the direction opposite from the reach determined by the oiiset. This feature allows adjustment of the offset reach by varying-the circuit elements of Fig. 4 without interfering in any way with the reach of the relay in theotherdirection so that readjustment aftersetting the offsetis not necessary. It will be obvious to those skilled in the art that a relay arrangementsuch as that-shown in Fig. 1 having characteristics such as are shown in Fig. Bis wellsuited for use asanrMl or an M2 unit for zones l and 2, and that the arrangement shown in I Fig. 4 having character istics such as those shown'inili'igfi is adapted for use as an M3 unit for third zone application.

While I have, in accordance with the patent statutes, shown and described my invention as applied to a particular-power system and as embodying various devices diagrammatically indicatecl, changes and modifications will b'e obvious to those skilled in the art, and I, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true scope and spirit "of my invention.

, thecycle of the one electrical quantity to super ate said device when the resultant voltage sup- 10 WhatI'claim-as new and de'sireto secure by Letters Patent of the United States is:

1. A mho relay arrangement for completing the trip circuit of a circuit interrupter in an electric power 's-ystempomprising an electronic device-having a'control grid and a suppressor grid, means for deriving from the power system'a voltage dependent on an electrical quantity of the system, 'means for deriving from the power system a voltage dependent on another electrical quantity of the system, means for shifting at least one of these voltages So that the two voltages are substantially out-of-phase during fault'rconditions,.means for comparing these two voltages and for supplying the resultant voltage toth'e control grid of said electronic device, and

means "for energizing the suppressor .grid oflsai'd' electronic device at apredetermined .instantin plied to the control grid thereof is of a predetermined value.

2. mA mho relay arrangement for completing the trip-circuit ofuacircuit interrupter in'an electric power' system comprising an electronic device havinga control grid and a suppressor grid, means torderiving from the powersystem a voltage-dependent on the :system voltage, means for deriving from the power system a voltage de-,

and means for energizing the suppressor grid 'of said electronic device when the instantaneous voltage o'f the system a maximum value to operate said device when the resultant voltage suppliedto thecontrol grid thereof of a ,pre-

determined value.

3.---A mho relay arrangement 'for completing the trip circuit of a circuit interrupter "in an electric power system comprising .an electronic "device having acontrol .grid and .ansuppressor grid, means forlderiving from thepower systema voltage dependent on the system voltage, means for deriving from .thepower system a voltage dependent on the system current, means for shifting at least one of these voltages so that the two voltages are substantially 180 out-of-phase during fault conditions, means for comparing these two voltages and for supplying the resultant voltage to the control grid of said electronic device,

and means for energizing the suppressorigrid of said electronic device when the instantaneous two last mentioned voltages and for supplyingthe combined voltage to the suppressor grid or said 'devicetocause said deviceto operate when the *conibmedinstantaneous vdltageis a maxitrol grid is indicative of a fault condition on the system. a

, 5. A mho relay for operating circuit interrupting means in an electric power system and having an offset impedance characteristic comprising electronic means, means for supplying an operating voltage to said electronic means during both the positive and negative half cycles of the system voltage, said operating voltage being derived from predetermined electrical quantities of the system, means for deriving two electrical quantities from the system dependent on the system voltage and current respectively, means for vectorially adding the two quantities derived from the system voltage and current, and means for supplying the vector sum of these two quantities to said electronic means during both the positive and negative half cycles thereof to render said electronic means conductive when the vector sum of such quantities is a maximum and whenan operating voltage indicative of a fault condition on the system is supplied to said electronic means.

6. Amho relay for affording protection for an electric power system and having an offset impedance characteristic comprising an electroresponsive device, means for supplying to said device a predetermined electrical quantity indicative of a fault condition on thesystem, means for deriving a voltage from the system dependent on the system voltage, means for deriving a voltage from the system dependent on the system current, means for combining the two derived voltages,'and means for supplying the combined volt-' age to said electroresponsive device to operate said device only at a predetermined instant in the cycle of said combined voltage and when the value'of the electrical quantity supplied to said device is indicative of a fault condition on the system.

'7. A mho relay for operating circuit interrupting means in an electric power system and having an offset impedance characteristic comprising two electronic devices each having a control grid and a suppressor grid, means for supplying the control grids with alternate half cycles of an operating voltage derived from the system voltage and current, meansfor deriving two electrical quantities from the system dependent on the system voltage and current respectively, means for combining said quantities, and means for supplying the positive half cycles of the resulting quantlty to the suppressor grid of one device and the negative half cycles of the resulting quantity to the suppressor grid of the'other device to operate each device when the resulting quantity is a max,- imum value and when an operating voltage indicative of a fault condition on said system is supplied to the control grids.

'8. A mho relay for afi'ording protection for an electric power system and having an offset impedance characteristic comprising an electroresponsive device, means for supplying to said device a predetermined electrical quantity indicativeof a fault condition on the system, means for deriving a voltage from the system dependent.

on the instantaneous value of the system voltage, means for deriving a voltage from the system dependent on the instantaneous value of the system current, means for vectorially adding these two voltages together, and means for supplying the vector sum of these voltages to said device to cause operation thereof when the instantaneous value of the vector'sum of these voltages is a maximum and when the value of the electri al quantity supplied to said device is indicative of v a fault condition on the system;

9. A relay for affording protection for an elec tric power system and having an oifset impedance characteristic comprising two electronic devices each having a control grid and a suppressor grid, means for supplying to the control grids of said devices alternate half cycles of a predetermined electrical quantity indicative of a fault condition on the system, means for deriving an electrical quantity from the system dependent upon the instantaneous value of the system voltage, means for deriving an electrical quantity from the system dependent upon the instantaneous value of the system current, and means for vectorially adding the derived quantities and for supplying alternate half cycles of the vector sum thereof to the suppressor grids of said device to cause operation thereof when the vector sum of the de- ..rived quantities is a maximum value and when the value of the electrical quantity supplied to the control grid is indicative of a fault condition on the system.

lot A relay arrangement for completing the? trip circuit of a circuit interrupter in an electric power system comprising an electronic devicehaving a control grid and a suppressor grid, a transformer for deriving from the power system a voltage dependent on the system voltage, a transactor for deriving from the power system a voltage dependent on the system current, means for shifting the phase relationship of the voltage derived by said transactor so that the two derived voltages'are substantially out-of-phase during fault conditions, circuit means for comparing the derived voltages and for supplying the resultant voltage to the control grid of said electronic device, and a pulsing circuit energized by said transformer for energizing the suppressor rid of said electronic device when the instantaneous voltage of the power system is a maximum value to cause said device to operate when the'voltage supplied to the control grid thereof is indicative of a fault on the power system.

11. A relay arrangement for completing the tripcircuit of a circuit interrupter in an elec* tric power system comprising an electronic device having a control grid and a suppressor grid, a transformer for deriving from the power sys tem a voltage dependent on the system voltage, a transactor for deriving from the power system a voltage dependent on the system current, means for shifting the phase relationship of the voltage derived by said transactor so that the two derived voltages are substantially 180 out-ofphase during fault conditions, circuit means for comparing the derived voltages and for supplying the resultant voltage to the control grid of the instantaneous voltage of the power system is a maximum value to cause said device to operate when the voltage supplied to the control grid thereof is indicative of a fault on the power system, and means for completing the trip circuit of the circuit interrupter in the power system circuit including a gas-filled tube connected in the trip circuit of the interrupter and a capacitor disposed between the plate terminal of said device and the cathode terminal of said gas-filled tube for causing said gass-filled tube to operate in response to operation of said device.

12. A relay arrangement having an offset impedance characteristic for completing the trip circuit of a circuit interrupter in an electric power system comprising an electronic device having a control grid and a suppressor grid, a transformer for deriving from the power system a voltage dependent on the system voltage, a transactor for deriving from the power system a voltage dependent on the system current, means for shifting the phase relationship of the voltage derived by said transactor so that the two derived voltages are substantially 180 out-of-phase during fault conditions, circuit means for comparing the derived voltages and for supplying the resultant voltage to the control grid of said electronic device, and a pulsing circuit energized by a voltage derived by said transformer and another voltage vectorially added thereto and derived by said transactor for energizing the suppressor grid of said electronic device when the instantaneous voltage supplied to said pulsing circuit is a maximum value to cause said device to operate when the voltage supplied to the control grid thereof is indicative of a fault on the power system.

13. A mho relay for affording protection for an electric power system comprising electronic means, means for deriving from the system a voltage dependent on the system voltage, means for deriving from the system a voltage dependent on the system current, means for shifting at least one of these voltages so that the two derived voltages are substantially 180 out-of-phase during fault conditions, means for comparing these two voltages and for supplying the resultant voltage to said electronic means, and means for supplying an energizing pulse to said electronic means at the instant when the system voltage is a maximum to cause said electronic means to operate if said resultant voltage is indicative of a fault condition on the system.

ALBERT R. VAN C. WARRINGTON.

REFERENCES CITED The following references are of record in the file of this patent or the original patent:

UNITED STATES PATENTS Number Name Date 1,967,850 Wideroe July 24, 1934 2,027,214 Wideroe Jan. 7, 1936 2,299,561 Bivens Oct. 20, 1942 2,399,322 Carlin Apr. 30, 1946 2,405,081 Warrington July 30, 1946 

